Transition metals are of increasing importance in a variety of electronic and electrochemical applications. This is because transition metals are excellent electrical conductors, are generally unreactive, and resist oxidation. In addition, late transition metals form stable interfaces with high dielectric constant materials and form good electrical contacts with other metals used for interconnection. Thus, the late transition metals have suitable properties for a variety of uses in the formation of integrated circuitry. They are, for example, suitable for use as electrodes in high-k and ferroelectric capacitors, and in metallization stacks and barriers between dielectric material and semiconductive material, such as silicon of semiconductor substrates in semiconductor integrated circuit devices.
One example integrated circuit semiconductor device is a field effect transistor having a gate construction which includes a conductive control gate region and a floating gate or charge trapping region. The floating gate or charge trapping region is received intermediate the control gate and a channel region, and is separated from each by non-conductive dielectric material. As device geometry continues to shrink, the dielectric material separating these regions become thinner. Such may undesirably result in leakage current flowing between the floating gate or charge trapping region through the dielectric material into the channel region, and thereby adversely effect operation of the device.
Late transition metals have been proposed for use as material in such gate stacks for either of the control gate or for the floating gate or charge trapping region. The gate constructions or stacks might be formed by patterning a mask into desired line shapes, and subsequently substantially anisotropically etching exposed unmasked regions of the gate stack materials to form the desired gate lines. Such, of course, requires etching of unmasked late transition metal material of such gate stack materials. However, late transition metals can be difficult to uniformly and selectively etch relative to other materials. Late transition metals, such as platinum, rhodium, iridium, palladium, copper cobalt, iron, nickel, silver, osmium, gold, and ruthenium, can be wet etched or ion milled. Halogen-containing gases, such as chlorine gas or hydrogen bromide, and oxygen have also been used to plasma etch platinum. Since the late transition metals are relatively unreactive, highly reactive etchants are often used. However, if during fabrication the integrated circuit includes other exposed materials such as main group metals, early transition metals, hard mask materials and/or photoresist materials, these highly reactive etchants can remove the other exposed materials at a faster rate than the late transition metal or damage the other exposed materials. Alternatively, high temperature etching is used to increase the etch rate of the unreactive late transition metal. However, other exposed materials, such as hard mask materials, photoresist, main group metals, early transition metals, are not usually compatible with high temperature, corrosive etches.
While the invention was motivated in addressing the above identified issues, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded, without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.